you forgot ....."in the rain, with loaded panniers"

I think discs are fantastic and the mechanical variants do not increase complexity at all compared to rim brakes.
As long as the wheels are properly built and the frame/fork is designed to accommodate the disc-specific loads, I feel discs are a much cleaner, better performing (particularly in inclement weather) and lower maintenance option.
Less wear on the rims, less frequent brake pad replacement..........

I've used top end rim brakes, and they do perform quite well.
I think discs are more practical and perform as well or better, and there is no contest in wet conditions. I was startled the first time I rode a disc-equipped bike in the wet. I instinctively applied more pressure (a learned trait from years of road/mtb riding with rim brakes) and damn near locked the wheels up the first time I stopped.
I've gotten accustomed to them, and they essentially offer consistent performance wet or dry.

Back to the jist of the thread, your budget opens tons of possibilities, and I'd think a build would offer you the flexibility to pick and choose what you want. You can often save money by "packaging" your build kit (Universal cycles comes to mind) or by cherry picking sales on the internet (pricepoint, bikeman, jensen, universal.......).